k-cell

A cell of rank k is also called a rank-k cell or k-cell. A 0-cell is an atom, a 1-cell is a list, a 2-cell is a table, and so on. If the rank of the cells of a noun is given, then the frame is whatever is left over of the shape of the noun.

Negative numbers are also used, as in _2-cell and _1-cell; the frames of such cells have length indicated by the magnitude of the numbers. You have seen _1-cells before: they are items.